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Aida Botonjić Tieto 1 WCDMA/HSPA Aida Botonjić
Aida Botonjić Tieto 1
WCDMA/HSPA
Aida Botonjić
Aida Botonjić Tieto 2
1990 2000
1st generation
Analogue speech
NMT, AMPS, TACS
2nd generation
Digital speech + low-rate data (<64 kbps)
GSM, PDC, IS-95,
IS-136 (D-AMPS)
Multimedia services (<2 Mbps)
+ 2nd gen. services
3rd generation
UMTS/IMT-2000
1980
Background
LTE
2010
Faster
Multimedia services (30-100Mpbs)
+ 3rd gen. services
4th generation
LTE
Aida Botonjić Tieto 3
3GPP releases
R99: WCDMA Evolved
R5: HSDPA – High Speed Downlink Packet Access
R6: HSUPA – Enhanced Uplink
LTE – Long-Term Evolution
Enhanced Uplink
(HSUPA) MIMO
CPC
Enhanced Downlink
(HSDPA)
Rel 4 Rel 5 Rel 6
HSPA WCDMA
R99 Rel 7 Rel 8
HSPA Evolution
LTE
= Third Generation Partnership Project
Aida Botonjić Tieto 4
Why WCDMA/HSPA?
• Applications: • E-mail
• Video telephony
• Web browsing
• Content sharing, e.g. Picture/video upload.
• Devices (UE): • Broadband modem
• Mobile phones with
• Large color screen
• Gbyte memories
• HSPA Targets: • Adapt to fast variations in radio conditions
• Reduced delays
• Improved High-Bitrate Availability
• Improved Capacity
Aida Botonjić Tieto 5
WCDMA network architecture
Node B
Node B
RNC RNC
dedicated channels
Iur
Iub
Iu
Core network
(Internet, PSTN)
UE
Aida Botonjić Tieto 6
Frame structure
#0 #1 #2 #3 #14
One slot, 2/3ms
One radio frame, 10 ms
#13
One subframe, 2ms
Time slot is the shortest repetitive period
Radio frame is the shortest transmission duration
Aida Botonjić Tieto 7
HSDPA Basic Principles
Shared Channel Transmission Dynamically shared in time & code
domain
Higher-order Modulation 16QAM in complement to QPSK for
higher peak bit rates
2 ms
Short TTI (2 ms) Reduced latency
Fast Hybrid ARQ with
Soft Combining Reduced round trip delay
Fast Radio Channel
Dependent Scheduling Scheduling of users on 2 ms time
basis
Fast Link Adaptation Data rate adapted to radio
conditions on 2 ms time basis
t
P
Dynamic Power Allocation Efficient power &
spectrum utilisation
= HS-DSCH
Aida Botonjić Tieto 8
HSUPA Basic Principles
Fast Retransmissions
Roundtrip time ~2 ms possible
Soft combination of multiple attempts
Fast Radio-Dependent Scheduling
2 ms time basis
2 ms
Short TTI (2 ms)
Reduced latency
= E-DCH
Aida Botonjić Tieto 9
Shared Channel
Transmission
A set of radio resources dynamically shared among multiple
users, in time and code domain
Efficient code utilization
Efficient power utilization
Channelization codes allocated
for HS-DSCH transmission
8 codes (example) SF=16
SF=8
SF=4
SF=2
SF=1
TTI
User #1 User #2 User #3 User #4
Shared
channelization
codes
time
Aida Botonjić Tieto 10
Fast Channel-dependent
Scheduling
Scheduling = which UE to transmit to at a given time instant and at what rate
Basic idea: transmit at fading peaks
May lead to large variations in data rate between users
Tradeoff: fairness vs cell throughput
high data rate
low data rate
Time
#2 #1 #2 #2 #1 #1 #1
Scheduled
user
User 1
User 2
TTI
Aida Botonjić Tieto 11
Fast Link
Adaptation
Adjust transmission parameters to match
instantaneous channel conditions
HS-DSCH: Rate control (constant power)
Adaptive coding
Adaptive modulation (QPSK or 16QAM)
Adapt on 2 ms TTI basis fast
Release 99: Power control (constant rate)
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Good channel
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less power
Bad channel
conditions
more power
power control
(HSUPA E-DCH)
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Good channel
conditions
high data rate
Bad channel
conditions
low data rate
rate adaptation
(HSDPA HS-DSCH)
Aida Botonjić Tieto 12
Higher Order
Modulation
16QAM may be used as a complement to QPSK
16QAM allows for twice the peak data rate compared to QPSK
16QAM
2 bits/symbol 4 bits/symbol
QPSK
Release 99: only QPSK
Aida Botonjić Tieto 13
Short 2 ms TTI
Reduced air-interface delay
Improved end-user performance
Necessary to benefit from other HS-DSCH features
Fast Link Adaptation
Fast hybrid ARQ with soft combining
Fast Channel-dependent Scheduling
10 ms
20 ms
40 ms
80 ms
Earlier releases
2 ms
Rel 5
2 ms
Aida Botonjić Tieto 14
ACK
TO RNC
Transmitter Receiver
Rapid retransmissions of erroneous data
• Hybrid ARQ protocol terminated in Node B
short RTT (typical example: 2 ms)
• Soft combining in UE of multiple transmission
attempts
reduced error rates for retransmissions
Fast Hybrid ARQ with Soft
Combining
Aida Botonjić Tieto 15
NACK
TO RNC
ACK
Transmitter Receiver
Fast Hybrid ARQ with Soft
Combining
Rapid retransmissions of erroneous data
• Hybrid ARQ protocol terminated in Node B
short RTT (typical example: 2 ms)
• Soft combining in UE of multiple transmission
attempts
reduced error rates for retransmissions
Aida Botonjić Tieto 16
Dynamic Power
allocation
Dedicated channels (power controlled)
Common channels
Power usage with dedicated channels
channels
t
Unused power
Power
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3GPP Release 99 3GPP Release 5
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Downlink channel with dynamic power allocation t
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Power
Dedicated channels (power controlled)
Common channels
HS-DSCH (rate controlled)
Aida Botonjić Tieto 17
Conclusion
Rel 99 HSPA (Rel 5 & 6)
Channel transmission in time
domain
Channel transmission in time and
space domain
Scheduling Channel dependent scheduling
QPSK modulation QPSK and 16 QAM modulation
TTImin= 10ms TTImin= 2ms
ARQ HARQ
Static power allocation Dynamic power allocation
- Link adaptation
